1. Field of the Invention
The present invention relates to Bordetella pertussis variants producing a non-toxic but immunogenic pertussis toxin mutant protein, which is applied for preparing a new pertussis vaccine.
More particularly, the present invention relates to a Bordetella pertussis phase I variant not having a pertussis toxic activity, but producing a partial antigen protein which induces an antibody for neutralizing the biological activity of pertussis toxin.
2. Description of the Related Art
The pertussis toxin has a molecular weight of about 107 KDa, and is composed of two functionally different parts (A and B) as the bacterial toxin, such as diphtheria toxin and cholera toxin. The part A (subunit 1, S1) is thought to be involved in NAD-dependent ADP-ribosyltransferase activity, and part B (subunit 2, 3, 4(2), 5, S2, S3, S4, S5) is involved in the binding to target cells. A variety of the following physiological activities thereof are known: namely, leukocytosis-promoting activity, histamine sensitizing activity, islet-activating activity, adjuvant activity, mitogen activity, glycerol-releasing activity, vascular permeability stimulating activity, and CHO cell-clustering activity. Based on these physiological activities, pertussis toxin is considered a major pathogenic factor in the occurrence of whooping cough, an infection having a serious effect on infants. Accordingly, pertussis toxin is recognized as an important protective antigen in the preparation of a corresponding pertussis vaccine.
In general it is important that toxic activity thereof is eliminated and the antigenicity thereof is maintained, to ensure the safety when preparing a pertussis vaccine consisting of such a toxic protein, and accordingly, the toxin is detoxified (i.e., toxoid formation) with agents such as formalin or glutaraldehyde, which modify the lysine residue. Recent reports of the gene cloning of pertussis toxin have demonstrated, however, that no lysine residue is contained in the active (i.e., NAD-dependent ADP-ribosyltransferase) site, due to the original toxic activity, and this means that the pertussis toxin is not sufficiently inactivated by the previous toxoid formation method. It is not clear whether or not the remaining toxic activity has an effect on the human body. Therefore, to avoid the above problems, the development of a pertussis toxoid having no biological activities but inducing an antibody for neutralizing the biological activities of pertussis toxin, is required.
Recently, biotechnology, particularly gene manipulation techniques, has been used as a method for an effective mass production of useful, physiologically active proteins. As previously set forth, the gene of pertussis toxin is also cloned, and some expressions are conducted using E. coli.
Nevertheless at the present time, this pertussis toxin consists of 5 subunits, and E. coli produces the recombinant pertussis toxin inside the cells. Thus many problems in industrial production remain.